From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751848AbcDJMgZ (ORCPT ); Sun, 10 Apr 2016 08:36:25 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:53371 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751077AbcDJMgY (ORCPT ); Sun, 10 Apr 2016 08:36:24 -0400 Date: Sun, 10 Apr 2016 08:35:49 -0400 From: Chris Mason To: Mike Galbraith CC: Peter Zijlstra , Ingo Molnar , Matt Fleming , Subject: Re: sched: tweak select_idle_sibling to look for idle threads Message-ID: <20160410123549.GA6046@clm-mbp.thefacebook.com> Mail-Followup-To: Chris Mason , Mike Galbraith , Peter Zijlstra , Ingo Molnar , Matt Fleming , linux-kernel@vger.kernel.org References: <20160405180822.tjtyyc3qh4leflfj@floor.thefacebook.com> <20160409190554.honue3gtian2p6vr@floor.thefacebook.com> <1460282661.4251.44.camel@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1460282661.4251.44.camel@suse.de> User-Agent: Mutt/1.5.24 (2015-08-30) X-Originating-IP: [192.168.52.123] X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-04-10_08:,, signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 10, 2016 at 12:04:21PM +0200, Mike Galbraith wrote: > On Sat, 2016-04-09 at 15:05 -0400, Chris Mason wrote: > > > This does preserve the existing logic to prefer idle cores over idle > > CPU threads, and includes some tests to try and avoid the idle scan when we're > > actually better off sharing a non-idle CPU with someone else. > > My box says the "oh nevermind" checks aren't selective enough, tbench > dropped 4% at clients=cores, and 2% at clients=threads. I knew this part would need more experimentation, so I kept v1 as simple as possible. On my box, tbench clients=cores is 5% faster, clients=threads is 4% faster. bounce_to_target() is a small version of task_hot(), I did get more accurate decisions by using the full task_hot(), so I can try that again. I'm testing on one of these: Intel(R) Xeon(R) CPU E5-2660 v2 @ 2.20GHz, which has two sockets and 10 cores per socket. What are you testing with? If it's two sockets or less I may be able to find one to reproduce with. > > > Benchmarks in production show overall capacity going up between 2-5% > > depending on the metric. > > Latency rules all loads certainly exist, and clearly want some love, > but the bigger the socket, and the more threads/core, the more that > traverse is gonna hurt the others, so seems either we need a better > filter, or a (yeah yeah, yet another damn) tweakable. > > Oh, and bounce_to_target() seems an odd way to say full_traverse. Sure, I can rename it. -chris